Heretofore numerous types of torque limiting clutches have been known. Typically, such clutches are physically large devices and necessarily so to achieve the capability of transferring force or torque below a certain threshold level, while limiting torque transmission by slippage or the like above such threshold. Previously, the size and complexity of the torque limiting clutch has been a direct function of the characteristic torque of the clutch.
Applicant presents that the state of the art in torque limiting clutches is best shown in his own prior U.S. Pat. No. 4,401,426 and the disclosure of co-pending patent application Ser. No. 346,296, filed Feb. 5, 1982, as a continuation-in-part of the aforementioned patent. As related to this application, such prior art teaches the use of spring bolt assemblies and spring pin assemblies in a torque limiting clutch. Such spring assemblies allow for ease of assembly while providing consistent characteristic torque over the wear life of the clutch. They further provide for a tamper-proof assembly.
Torque limiting clutches typically are of a single disc construction, requiring large friction plates to achieve the desired characteristic torque, greatly increasing the size, mass, and manufacturing cost, all to the detriment of the user. Known torque limiting clutches are also susceptible to degradation by heat build up and may cause fire or explosion when operated in volatile environments.